The 25 square-mile Hanford 100-Area (USDOE) site is located 35 miles north of Richland, Washington. It is one of four areas at the Hanford Nuclear Reservation (Hanford) originally listed on EPA's National Priorities List (NPL). These areas are part of a U.S. Department of Energy (DOE) complex that includes buildings, disposal sites, a national monument and other vacant land totaling about 586 square miles. The 100-Area cleanup is focused on contamination that originated from nine nuclear reactors, the last one shutting down in 1988. Cooling water contaminated with radioactive and hazardous chemicals was discharged to both the adjacent Columbia River and infiltration cribs and trenches. Site operations also included burying contaminated solid wastes on-site. These activities contaminated soil, sludge and groundwater with radioactive constituents, heavy metals and other hazardous chemicals. EPA has divided the site into several cleanup areas, or operable units (OUs) to better address site contamination. Final remedies have not yet been selected for the site�s OUs; however, eight interim remedies have been selected and remedial investigations are underway to support selection of the site�s final remedy.